package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MapperStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import javax.sql.DataSource;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {

    private Configuration configuration;
    private DataSource dataSource;

    public SimpleExecutor(Configuration configuration) {
        this.configuration = configuration;
        this.dataSource = configuration.getDataSource();
    }

    @Override
    public <E> List<E> query(MapperStatement mapperStatement, Object... params) throws Exception{
        //1.注册驱动、获取连接
        Connection connection = dataSource.getConnection();

        //2.获取sql语句
        String sql = mapperStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4.设置参数
            //获取参数的全路径
        String paramterType = mapperStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++){
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1, o);

        }
        preparedStatement.execute();
        //5.执行SQL
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mapperStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //6.封装返回结果集
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i < metaData.getColumnCount(); i++){
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //使用反射或内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }

        return (List<E>) objects;
    }

    @Override
    public int update(MapperStatement mapperStatement, Object param) throws Exception {
        Connection connection = dataSource.getConnection();
        BoundSql boundSql = getBoundSql(mapperStatement.getSql());
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        Class<?> paramterClass = getClassType(mapperStatement.getParamterType());

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++){
            String content = parameterMappingList.get(i).getContent();
            Field declaredField = paramterClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(param);
            preparedStatement.setObject(i+1, o);
        }

        return preparedStatement.executeUpdate();
    }

    @Override
    public int deleteById(MapperStatement mapperStatement, Integer id) throws Exception {
        Connection connection = dataSource.getConnection();
        BoundSql boundSql = getBoundSql(mapperStatement.getSql());
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        if(id == null){
            throw new NullPointerException("参数为空,你确定不是来捣乱的吗？");
        }
        preparedStatement.setObject(1, id);
        return preparedStatement.executeUpdate();
    }

    private Class<?> getClassType(String paramterType){
        if(paramterType != null){
            try {
                Class<?> aClass = Class.forName(paramterType);
                return aClass;
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    /**
     * 完成对#{} 解析工作
     *  1.将#{}使用?进行替代
     *  2.解析出来#{}里面的值进行存储
     * @param sql
     * @return BoundSql
     */
    public BoundSql getBoundSql(String sql){
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;
    }
}
